Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers

Definitions

• the invention relates processes for making ethylene inter/polymers and the polymers that can be made by such processes as well as electrical devices containing such interpolymers.
• the invention relates especially, but not exclusively, to processes for making ethylene interpolymers at relatively high polymerization temperatures of over 100°C in order to form polymers with high levels of long chain branches (LCB); and especially such polymers having a relatively low density and a moderate molecular weight that are processable as a thermoplastic material.
• the high LCB can be expressed in terms of a Melt Index Ratio (MIR) of melt viscosities measured under different loads.
• MIR Melt Index Ratio
• the invention also relates to electrical devices having an insulating layer of the interpolymer or compositions containing such interpolymer such as electrical cables.
• plastomers Lower density ethylene interpolymers with moderate molecular weights will be referred herein as plastomers.
• Plastomers have been made with catalyst systems based on Ziegler-Natta vanadium catalysts using aluminum alkyl based activators. Such polymers have high levels of regio-inversion for the insertion of the propylene comonomer.
• the low activity of the catalyst leads to the need to de-ash the polymer to remove vanadium residues, especially for if the polymer is to be used for electrical applications.
• Propylene and 1 -butene have been used as comonomers to provide short chain branching (SCB) in Ziegler- Natta produced plastomers.
• SCB short chain branching
• metallocene based single site catalysts have been identified to make plastomers in a continuous solution process at higher temperatures and at higher activities where activity is defined as the amount of polymer produced per amount of transition metal single site catalyst component.
• metallocene based catalyst systems produce terminal unsaturation by, for example, beta-hydride elimination. It has been recognized that for many metallocene based processes the unsaturated chain end may incorporate in a growing chain and form long chain branches (LCB).
• LCB long chain branches
• EP495099 uses a hafnocene in conjunction with alumoxane as an activator.
• 1-octene, 1 -butene and propylene were used as a comonomer for batch polymerization at temperatures less than 100° C providing polymers with high MIR values. Extensive depletion of comonomer in batch type reactions may favor LCB formation.
• the polymerization conditions however lead to significant levels of catalyst residues.
• the polymer produced at the end of the batch polymerization process may have a significantly different comonomer content than that produced early in the process and the polymer may have a broader compositional distribution.
• octene-1 is used as a comonomer. Polymerization was at 170° C for MI levels of from 0.49 to 3.6 g/10 min. WO9945041 does not teach the use of propylene as a comonomer at especially high temperature polymerization temperatures.
• WO0234795 describes a plant, in which these processes can be practiced industrially and in which an advantageous arrangement is described for recycling unreacted monomers back to the polymerization reactor(s) after suitable purification through liquid phase separation, distillation and/or sieves.
• the above references are incorporated by reference for US purposes.
• WO0037514 describes a gel-free, branched semi-crystalline ethylene propylene copolymer containing high levels of propylene. The polymerization temperature was less than 100° C. In the examples a bridged zirconocene is used with an NCA in a continuous polymerization reactor.
• Ethylene propylene co-polymers and EP(D)M terpolymers having polyethylene type crystallinity are commercially used in medium voltage electrical insulation compounds. These compounds are applied as an insulation member over either a metallic conductor or a semi-conductive substrate in a multi- step extrusion process.
• the cable containing the insulation is typically vulcanized in a continuous vulcanization (CN) tube by the application of steam and hot water.
• Cross-linking packages may use silanes or peroxides as the active cross-linking ingredient.
• Metallocene catalyst based ethylene alpha-olefin copolymers also find limited application in electrical insulation compounds.
• Some ethylene-butene plastomer products made in a high-pressure process have been evaluated in insulation and semi-conductive formulations, see US6270856 (ExxonMobil, Hendewerk et al.) These polymers possess inherently good electrical insulating properties, but have a narrow molecular weight distribution (MWD) resulting in processability disadvantages.
• MWD molecular weight distribution
• Other plastomers made in solution processes have some LCB for reasons explained above.
• WO03000740 (ExxonMobil, Pehlert) suggests the use of modified NCA's to improve dielectric loss properties.
• ethylene-octene plastomers are produced at 140° C.
• WO9406858 discloses ethylene octene copolymers with moderate LCB.
• WO9732922 uses rheology-modification to increase branching levels.
• the resulting polymers have ⁇ 0.5% gel, a composition distribution breadth index >50%, and an molecular weight distribution Mw/Mn ⁇ 4.0. The above references are incorporated by reference for US purposes.
• Alpha-olef ⁇ n ethylene copolymers have been used in blends, especially with ethylene propylene vinyl norbornene terpolymers, see Rubber World, Volume 226, No. 2, pages 39 to 50.
• a continuous polymerization process for preparing a random ethylene interpolymer which comprises the steps of: (A) polymerizing ethylene, and an ⁇ -olefin comonomer selected from the group consisting of propylene and 1 -butene and mixtures thereof under continuous random polymerization conditions in the presence of single site catalyst system employing an ionic activator having cyclic ligands shielding a central charge bearing atom, at a temperature of 140° C to 250° C at a conversion of ethylene of 80 to 99% and a comonomer conversion offrom 20 to 80%; and (B) devolatilizing the polymer to provide an ethylene copolymer having a ddeennssiittyy ooff ffrroomm 00..8855 ttoo 00..9922 gg//ccrmr 3 , an MI of from 0.1 to 20 g/10 min and an MIR (I 2 )
• I 21 /I 2 values are a function of MI and at low
• MI value high values of MIR (I II ) are possible.
• the comonomer conversion may be less than 60 % and the MIR (I 21 /! 2 ) may be less than 180.
• the use of the lower ⁇ -olefin comonomers like propylene and butene are generally supplied from purer streams with lower catalyst poisons and permits higher polymerization activities. Higher activities result in lower catalyst residues in the final polymer product. Internal olefin byproducts, made during higher alpha-olefin production, may negatively impact catalyst activity and lead to higher catalyst residues.
• the interpolymer contains at least 55 mol % of ethylene derived units, preferably at least 60 mol % and especially at least 65 mol %; from 0 to less than 10 mol % of an ⁇ -olefin comonomer other than propylene and/or 1 -butene, preferably less than 5 mol %, and/or from 0 to less than 0.5 mol % and preferably less than 0.1 mol % of a diene.
• the predominance of ethylene and the use of lower ⁇ -olefin comonomer assist in efficient production of the desired highly processable polymer with reduced catalyst residue content.
• the polymerization may be performed adiabatically using a catalyst system including a hafnocene having two cyclopentadienyl groups connected by a bridging structure, preferably a single atom bridge.
• the ionic activator preferably has at least two polycyclic ligands, especially at least partly fluorinated.
• the use of a highly active metallocene catalyst and substantially equimolar ionic activator may permit reduced catalyst residue, which in turn may improve the electrical insulating properties.
• the reactor temperature may improve the amount of LCB through better incorporation of vinyl terminated polymer chains formed earlier in the polymerization process.
• Chain transfer agents such as hydrogen can influence the termination mechanism to reduce the amount of vinyl unsaturation and discourage LCB formation.
• the heat of the polymerization reaction may raise the temperature by at least 100° C between the feed for the continuous polymerization and the effluent to be devolatilized.
• the polymerization may be preformed in a single reactor such as a continuous stirred tank reactor or the polymerization may be perforaied in a series reactor to provide a multimodal molecular weight distribution, or a broad composition distribution.
• an ethylene interpolymer containing as ⁇ -olefin comonomer propylene and/or 1 -butene having a density of from 0.85 to 0.92 g/cm3, an MI of from 0.01 to 100 g/10 min and an MIR (I 21 /I 2 ) of from 30 to 400 obtained by solution polymerization using transition metal complex as a catalyst and a non-coordinating anion to provide a level of NCA derived residue as determined by boron content less than 0.5 ppm as determined by ICP, preferably undetectable by ICP.
• the polymer may display the same preferred polymer features as indicated when discussing the previous aspect.
• the MIR (121/12) is then suitably at least 45.
• the interpolymer may have specific MI ranges combined with specific high load/ low load MI ratio ranges.
• the MI is from 0.01 to 0.30, 121/12 > -103.45 x MI + 91.0 and/or 121/12 ⁇ -103.45 x MI + 241.0.
• the MI is from 0.30 to 1.40, 121/12 > -18.18 x MI + 65.4 and/or 121/12 ⁇ -18.18 x MI + 215.4.
• the MI is from 1.40 to 8.0, 121/12 > -1.515 x MI + 42.1 and/or 121/12 ⁇ -1.515 x MI + 192.1.
• the MI is from 8.0 to 1000, 121/12 > 30.0 and/or 121/12 ⁇ 180.0.
• the preferred process conditions may be obtained using as the single site catalyst is a transition metal complex of a Group IV metal, preferably Zr or Hf, most preferably Hf.
• a level of single site residue as measured by the content of transition metal may be reached which is less than 2 ppm (parts per million), preferably less than 1 ppm as determined by ICP.
• the density is suitably at least 0.85 and/or less than 0.9 and preferably at least 0.86 and/or less than 0.89. It is advantageous in electrical applications that the polymer contains from 0 to 0.1 wt % of an anti- agglomeration additive, such as a stearate salt.
• an anti- agglomeration additive such as a stearate salt.
• the invention provides an electrical device comprising an electrical conductor and a polymeric insulating layer comprising a polymer with any one or more of the features indicated previously or resulting from the process indicated previously.
• Compositions may be used for the insulting layer including the polymer of the invention in combination with other polymers, fillers etc. as may be desired for the particular electrical application under consideration.
• the insulating layer is of a composition also comprising an ethylene propylene elastomer with a Mooney [(1+4) 125° C] range of from 10 to 100 and optionally a diene.
• the elastomer is an ethylene- propylene-vinylnorbomene terpolymer, most preferably with a content of ethylene derived units of from 68-75 wt. %, a molecular weight distribution Mw/Mn of at least 5 and contains from 0.1 to 2.5 wt% of units derived from vinyl norbornene (VNB). Insulating layers may be obtained having a tensile strength of from 5 to 10 MPa min.; a break elongation of from 150 to 450% and a dielectric constant of less than 4.
• the polymerization conditions can be selected to provide a high conversion of the monomers in solution, so favoring the incorporation of vinyl terminated macromers, which thus go on to form LCB's. High conversions reduce the cost for recycling unconsumed monomer.
• the level of comonomer may be varied to target the desired density, melting point and heat of fusion.
• the density is at least 0.86, and/or preferably less than 0.9; above that which is usually applicable to EP copolymers made using vanadium catalysts.
• the LCB content may be indirectly measured by the melt index ratio, MIR measured at MIR (121/12) .
• Highly branched products have high MIR (121/12) and linear products have low MIR (121/12).
• substantially linear products may have moderate MIR (121/12) values around 12 to 17 as described in EP608369, and whereas typical commercial plastomers produced in solution, may have MIR (121/12) values that are somewhat above that, the plastomer products of this invention have MIR (121/12) values around 40 to 60 and even as high as 80.
• the high LCB content of these materials improves processability in extrusion and especially in the demanding application of extruding wire and cable insulation.
• the use of branch forming diene comonomers and/or presence of processing aids may be reduced or even avoided.
• the high level of LCB leads to improved processing while the polymer at the same time has a higher filler holding capability, lower catalyst residues and lower dielectric power loss.
• the process envelope for continuous solution polymerization reactor is limited by a number of mostly interrelated process aspects. If the catalyst activity is too low, the polymer will contain potential triggers for dielectric breakdown. Activity is conventionally expressed in terms of the amount of polymer produced per the amount of transition metal component consumed. Associated activators may be used at different molar ratios relative to the transition metal component. Thus for a full activity picture, the activity in terms of activator consumption per unit polymer produced may also be considered.
• the level of long chain branching depends on the selection of the transition metal component and some process conditions such as temperature and the extent to which the monomer present is converted.
• transition metal component and NCA may influence the chain growth and molecular weight. If the catalyst system and process conditions are selected to optimize molecular weight, higher operating temperature may be used to achieve a given MI. The higher operating temperature may increase the activity and/or permit higher polymer concentrations in the reactor and so higher productivity in terms of weight of polymer produced per unit time in a given size plant. The higher process temperature aids the incorporation of vinyl tenninated macromers.
• the level of branching is also influenced by the extent to which monomer is converted into polymer. At high conversions, where little monomer remains in the solvent, conditions are such that vinyl terminated chains are incorporated into the growing chains more frequently, resulting in higher levels of LCB. Catalyst levels may be adjusted to influence the level of conversion as desired.
• NCA it is most preferred to use a NCA whose charge bearing atom or atoms, especially boron or aluminum, are shielded by halogenated, especially perfluorinated, cyclic radicals, and especially polycyclic radical such as biphenyl and/or naphthyl radicals.
• the NCA is a borate precursor having a boron atom shielded by four, perfluorinated polycyclic radicals.
• Selected metallocene-NCA combinations may assist in preserving higher molecular weights and/or higher operating temperatures. Thus they may be among the preferred catalyst for the interpolymers of the invention.
• the invention provides an electrical device comprising an electrical conductor and a polymeric insulating layer comprising a polymer with any one or more of the features indicated previously or resulting from the process indicated previously.
• Compositions may be used for the insulting layer including the polymer of the invention in combination with other polymers, fillers etc. as may be desired for the particular electrical application under consideration.
• the insulating member comprising the polymer with the features described previously can be used in various wire an cable applications. These consist of low voltage, typically less than 5 kV, medium voltage, in the range of 5 kV to 69 kV and high voltage, describing range above 69 kV applications.
• the compounds in general comprise a reinforcing filler, such as calcined clay to provide mechanical properties and processability.
• a reinforcing filler such as calcined clay to provide mechanical properties and processability.
• the amount of filler used in the formulation depends on the type of application. Sometimes a flame retardant filler, such as magnesium hydroxide, is used in combination or replacing the calcined clay.
• the insulating member comprising the polymer with the features described above can also be used in flame retardant compound applications, wherein an inorganic filler containing water of hydration is used to provide flame retardant properties.
• Formulations for medium voltage applications are invariably formulated with lead oxide, that seemingly provides good electrical properties after aging. However, reduction or elimination of lead is desirable from environmental considerations.
• the insulating member comprising the polymer with features described previously can be used in compounds that are lead free or contain reduced amounts of lead.
• the formulations are designed without filler to minimize electrical loss.
• the polymer described previously can be used in combination with other polymers to furnish an unfilled compound that has adequate mechanical properties and processability.
• the insulating layer is of a composition also comprising an ethylene propylene elastomer with a Mooney [(1+4) 125° C] range of from 10 to 100 and optionally a diene.
• the elastomer is an ethylene- propylene-vinyl norbornene terpolymer, most preferably with a content of ethylene derived units of from 68-75 wt. %, a molecular weight distribution Mw/Mn of at least 5 and contains from 0.1 to 2.5 wt% of units derived from vinyl norbornene (VNB). Insulating layers may be obtained having a tensile strength of from 5 to 10 MPa min.; a break elongation of from 150 to 450% and a dielectric constant of less than 4.
• ***ICP-AES is a commercially available form of optical emission spectrometry with inductively coupled plasma.
• the plasma is formed by argon gas flowing tlirough a radio frequency field where it is kept in a state of partial ionization; i.e. the gas contains electrically charged particles. This allows it to operate at very high temperatures of up "to 10 000 C. At those conditions most elements emit light of characteristic wavelengths which can be measured and used to determine the concentration of particular elements.
• the sample to be analyzed is introduced into the pla-sma as a fine droplet aerosol.
• Light from the different elements is separated into different wavelengths by means of a grating and is captured by light-sensitive detectors, one for each element being analyzed. This permits simultaneous analysis of up to 40 elements.
• the sensitivity is comparable to flame atomic absorption with detection limits typically at the ⁇ g/L level in aqueous solutions.
• Copolymerizations were carried out in a single-phase, liquid-filled, stirred tank reactor with continuous flow of feeds to the system and continuous withdrawal of products under equilibrium conditions. All polymerizations were done in system with a solvent comprising predominantly C6 alkanes, referred to generally as "hexane" solvent, using soluble metallocene catalysts and discrete, non-coordinating borate anion as co-catalysts. An homogeneous dilute solution of tri-n-octyl aluminum in hexane was used as a scavenger in concentrations appropriate to maintain reaction. No transfer agents, such as hydrogen, were added to control molecular weight.
• the hexane solvent was purified over beds of 3 A mole sieves and basic alumina. Ethylene and octene were dried over beds of 3 A mole sieves only. All feeds were pumped into the reactors by metering pumps, except for the ethylene, which flowed as a gas through a mass flow meter/controller. Reactor temperature was controlled adiabatically by controlled chilling of the feeds and using the heat of polymerization to heat the reactor. Feed temperature can range from -20° C to 40° C or higher. Typical feed temperatures are kept at 10° C for high conversion runs and as high as 25° C for high temperature runs.
• the reactors were maintained at a pressure in excess of the vapor pressure of the reactant mixture to keep the reactants in the liquid phase. In this manner the reactors were operated liquid full in a homogeneous single phase. Ethylene and propylene feeds were combined into one stream and then mixed with a pre-chilled hexane stream. A hexane solution of a tri-n-octyl aluminum scavenger was added to the combined solvent and monomer stream just before it entered the reactor to further reduce the concentration of any catalyst poisons. A mixture of the catalyst components in solvent was pumped separately to the reactor and entered through a separate port.
• reaction mixture was stirred aggressively using a magna-drive system with three directionally opposed tilt paddle stirrers set to about 750 rpm to provide thorough mixing over a broad range of solution viscosities. Flow rates were set to maintain an average residence time in the reactor of about 10 minutes. On exiting the reactor the copolymer mixture was subjected to quenching ⁇ , a series of concentration steps, heat and vacuum stripping and pelletization. [0045] The general conditions may be as described in WO 599/45041 incorporated herein for US purposes. Water is then supplied to kill the polymerization reaction, which might otherwise continue in the presence of surviving catalyst, unreacted monomer, and elevated temperature.
• the temperature is raised to an extra-elevated level by the use of a selected catalyst system.
• the catalyst system is selected to provide a good high temperature stability and to incorporate comonomer and macromer readily.
• differences in incorporation of comonomers and/or macromers due to molecular size are reduced favoring LCB production.
• monomer and comonomer conversion can be increased limiting the amount of monomer and comonomer available for polymerization ar d again favoring macromer incoiporation and LCB formation.
• Increased temperatures can be reached in adiabatic opeiration by increasing the amount of monomer and comonomer converted to polymer- per unit time using increased levels of catalyst and increased monomer concentrations.
• Increased polymerization temperatures may themselves be associated with increased activity so that the catalyst addition rate may need to be changed to reach stable operating conditions.
• Increased monomer conversions may be reached by increasing catalyst levels or increasing the reactor residence times without increasing the monomer concentration so that monomer is consu-med to a greater extent and its concentration lowered.
• the catalyst system is selected to permit both higher monomer conversion and maintained or improved operating temperatures.
• Octene used as comonomer may include isomers. which have a negative effect on activity.
• Table 5 Specific values from samples during run
• Table 4 illustrates that using the dimethyl anilinium tetrakis
• Example I shows a high conversion and reasonable activity.
• Example II is made at a high polymerization temperature at some reduction in conversion.
• the MIR (121/12) at 46 remains high and activity is much higher than for I.
• Example III shows that the use of catalyst (B) permits a higher conversion/temperature balance than catalyst (A) at comparable activity.
• the choice of process conditions and catalyst permits the combination of a high conversion, high polymerization temperature and high MIR (121/12).
• Example IV and V show that using octene- 1 as a comonomer does not permit a good combination of high activity and high MIR (121/12).
• Table 6 contains a list of the ethylene ⁇ -olefin polymers used in the medium voltage electrical formulation also containing Vistalon V1703P commercially available from ExxonMobil Chemical company. This polymer contains vinyl norbornene (VNB) as the termonomer and is highly branched.
• VNB vinyl norbornene
• Metallocene polymers IV and VI are comparative ethylene octene polymers made with dimethyl anilinium tetrakis (pentafluorophenyl) borate as an activator at a density of 0.870.
• Ill is an inventive ethylene propylene copolymer prepared using a metallocene catalyst and dimethyl anilinium tetrakis (heptafluoro -naphthyl) borate as activator.
• Engage 8100 is an ethylene octene copolymer commercially available from DuPont Dow Elastomers LLC.
• Table 7 shows an industry standard medium voltage insulation compound containing 60 parts of clay as filler.
• the clay, Translink 37 is calcined, surface treated Kaolin available from Engelhard Corp.
• the formulations were compounded using a two pass mixing protocol in a 1600 ml. Banbury mixer using a batch weight of 1420 g, which corresponds to a fill factor of 75 %.
• the masterbatch compound without the peroxide was mixed in the first pass for a total mixing time of 7 minutes following the mixing procedure shown in Table 8.
• the masterbatch discharged from the Banbury mixer was sheeted out on a two-roll mill. The batch was homogenized several times on the mill. The mill temperature was maintained around 90° C during mixing. The milled masterbatch was cut into small strips using a mill knife.
• the screw length to diameter (LID) for this extruder is 20/1.
• the extruder screw has a compression ratio of 2/1, which is typical for processing rubber compounds.
• a cylindrical die with a land length of 9.5 rnm and diameter of 3.2 mm was used to assess surface appearance of the extrudates.
• the various zones of the extruder and the die block temperature are maintained constant at 125 °C.
• Granulated rubber is fed through the extruder hopper to maintain a full screw, but an empty hopper during extrusion.
• the extruder screw speed is varied from 25 RPM to 100 rpm.
• the mass throughput is measured at every screw speed by collecting a sample of the extrudate over a specific length of time, typically 10 to 30 seconds depending on the screw speed. At least three samples are collected to provide an average value. [0062] The surface roughness of the extrudate is analyzed using a Surfcom
• the Surfcom instrument is equipped with a diamond stylus that traverses over the surface of the extrudate under examination, recording the surface irregularities.
• the vertical distance between the highest and lowest point in a surface irregularity, denoted as Rt (Dm) is measured for every sample.
• the arithmetic mean Ra, denoting the departure of the surface profile from a mean line is also recorded (Dm).
• An average value is obtained based on at least 3 measurements per sample.
• Table 9 shows the compound cure and physical properties of medium voltage compound formulations,_prepared as outlined in Tables 7 and 8, containing the EP(D)M- VNB terpolymer V 1703P by itself and in blends with the metallocene ethylene propylene copolymer III.
• Formulation example 1 is a comparative formulation, while Formulation examples 2 through 4 are inventive compounds. Substitution of V 1703P with the metallocene candidate III leads to a marginal decrease in cure rate from the replacement of the VNB terpolymer, but enhanced heat aged physical properties, notably elongation to break. [0066] Table 10 shows compound extrusion properties of the formulation described in Table 9. Table 10
• FIG. 1 shows the variation of the compound dissipation (or loss) factor with time on samples that were aged in water at 90 °C.
• the performance of the inventive formulations 2 through 4 is very similar to the comparative formulation example 1.
• Table 11 shows the process conditions for the wire line extrusion, which correspond to typical run conditions of the control compound featuring the V 1703P polymer.
• the medium voltage insulation compound coating the wire was vulcanized in the steam / water heated continuos vulcanization tube maintained at a constant temperature of 208 °C.
• Typical residence time in the vulcanization tube depends on the line speed. At a line speed of 12.2 m/min, the residence time is 1.65 minutes.
• M313101 corresponds to run III.
• Table 12 shows the physical properties of the wire samples of
• Table 11 containing varying blend ratios of the metallocene candidate M3013101 to V 1703P.
• Formulation example 8 is the control formulation featuring V 1703P without the metallocene candidate.
• the surface roughness of the wire samples (Rt) is nearly the same in all the compounds.
• the melt fracture seen in Formulation examples 5 and 6 on extruded compounds (Table 10) is eliminated by the application of steam in the continuous vulcanization tube. All the example formulations 5 though 7 achieve close to 90 % cure, comparable to the control Example 8.
• the tensile strength of the inventive compounds is slightly lower than the control, but this level is adequate for the end use application.
• TABLE 12 PROPERTIES OF EXTRUDED WIRE
• the processes. Polymers, and formulations described herein enable the production of compositions and electrical devices capable of exhibiting beneficial electrical properties in the absence of a lead oxide compound or at reduced levels of a lead oxide compound.
• the beneficial electrical properties are dissipation factors and dielectric constants.
• Table 13 lists three medium voltage compound formulations, prepared as outlined in Tables 7 and 8, for which the electrical properties were evaluated. Each formulation includes an ethylene interpolymer identified as Polymer IV or Polymer V.
• Polymer IV is an EPDM terpolymer produced in a Ziegler-Natta catalyzed polymerization.
• Polymer IV has a Mooney viscosity of ML (1 + 4) at 125° C of 25.
• the terpolymer incorporates ethylene, propylene, and ethylidene at weight percentages of 73.3 wt.%, 23.4 wt.%, and 3.3 wt.%, respectively.
• Polymer IV is commercially available from ExxonMobil Chemical under the designation Vistalon® 8731.
• Polymer V is an EPM copolymer (ethylene-propylene copolymer) produced using a continuous polymerization process incorporating a metallocene catalyst and dimethyl anilinium tetrakis (heptafluoro-naphthyl) borate as activator.
• Polymer V has a Mooney viscosity of ML (1 + 4) at 125° C of 16 and a melt index of 1 (g/10 min.).
• Polymer V incorporates ethylene and propylene at weight percentages of 72 wt.% and 28 wt.% respectively. Table 13
• Dissipation factors for Examples 9-11 were determined over time as reported in Table 14. Dissipation factors were determined after aging in water at 90° C in accordance with ASTM D-150-98.
• the dissipation factors over time for the formulations of Examples 9-11 are plotted in FIG. 3.
• the formulation incorporating Polymer IV demonstrated improved dissipation factor properties resulting from the inclusion of 5 phr of a lead oxide compound (ERD 90).
• the formulation of Example 11, incorporating metallocene catalyzed Polymer V demonstrated superior dissipation factor performance even without the addition of or presence of lead, or a derivative thereof, such as a lead oxide compound.
• the formulations described herein are substantially free of lead, and derivatives thereof.
• the term substantially free of lead and derivatives thereof shall mean formulations having less than .1 phr lead and/or derivatives thereof, including, but not limited to lead oxides, per 100 phr polymeric material(s) in the composition.
• the formulations described herein are substantially free of lead, and derivatives thereof and have dissipation factors of less than 0.02 after aging for 28 days in water at 90° C.
• the formulations described herein are substantially free of lead, and derivatives thereof, and have dissipation factors of less than 0.15 after aging for 28 days in water at 90° C.
• the formulations described herein are substantially free of lead, and derivatives thereof, and have dissipation factors of less than 0.13 after aging for 28 days in water at 90° C.
• Dielectric constant values of the formulations of Examples 9-11 were determined over time as reported in Table 15. Dielectric constant values were determined after aging in water at 90° C in accordance with ASTM D-150- 98. Table 15
• the lower the dielectric constant the better the electrical property of the formulation.
• the formulations of Examples 9 and 10, incorporating Polymer IV, with and without incorporation a lead oxide exhibited relatively stable dielectric constants over the 28-day period.
• the formulation of Example 11 incorporating the metallocene catalyzed copolymer, Polymer V, and no added lead oxide, demonstrated a superior lower dielectric constant after one day and a favorable dielectric constant reduction of more than 5% by the end of the 28 day period.
• the formulations described herein are substantially free of lead, and derivatives thereof, and have dielectric constant values of less than 2.55 after aging for 28 days in water at 90° C.
• the formulations described herein are substantially free of lead, and derivatives thereof, and have dielectric constant values of less than 2.50 after aging for 28 days in water at 90° C. In still other embodiments, the formulations described herein are substantially free of lead, and derivatives thereof, and have dielectric constant values of less than 2.45 after aging for 28 days in water at 90° C.
• Tradenames used herein are indicated by a ⁇ symbol ,or an ® symbol, indicating that the names may be protected by certain trademark rights. Some such names may also be registered trademarks in various jurisdictions.
• All patents, test procedures, and other documents cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

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